The present invention relates to a device for determining when a pregnant female mammal has begun the first phase of labor. More particularly, the present invention relates to a sensor device which is implanted in the female""s cervix and which is capable of sensing dilatation of the cervix at the onset of labor and of transmitting a warning signal to an auxiliary electronic device.
It is often difficult for a pregnant woman to know when labor has begun. For example, during the last trimester of pregnancy, false labor comprising irregular and shallow contractions of the uterus, the so-called xe2x80x9cBraxton Hicks contractionsxe2x80x9d, may be confused with actual labor. Unlike true labor, these contractions are highly irregular and may be felt in the abdomen at onset rather than in the back. Furthermore, Braxton Hicks contractions are weak and do not strengthen. Despite these distinguishing characteristics, many women, especially those lacking competent care, may not be able to tell the difference between false labor and actual labor.
During the latent phase of labor (pre labor), the cervix begins thinning out and may dilate very gradually. The first stage of labor is generally considered to begin when the cervix starts to open and ends when it is fully open. Women are admitted to the hospital when the dilation of the cervix reaches about 4 cm. The vagina may be examined to determine if the membranes surrounding the fetus have ruptured and to measure how dilated and effaced the cervix is. To save the woman""s energy and to avoid tearing her cervix, pushing is discouraged during the first stage of labor which may last anywhere from a few hours to 12 hours. Pushing efforts are needed during the second stage of labor which begins when the cervix has achieved a maximum dilation of about 10 cm.
In some instances, rupture of the fluid-filled membranes surrounding the fetus may occur before labor begins (the water breaks), causing leakage of the amniotic fluid through the cervix and vagina and requiring immediate medical attention. In most of these cases, labor spontaneously begins within 24 hours from the time the water breaks. In cases where labor fails to begin, labor is induced to prevent infections caused by bacteria entering the uterus from the vagina. Because the release of the amniotic fluid does not always occur as a sudden gush and may be a slow trickle resembling urinary leakage, a woman may not always be sure that her water has broken and she may fail to seek medical attention promptly. This delay may cause stress to the fetus and may endanger the health of mother and child.
xe2x80x9cSilent laborxe2x80x9d is a situation in which labor onset occurs without pronounced contractions. This condition occurs commonly in premature birth situations where dilatation and effacement of the cervix are not accompanied with contractions. In some cases, contractions may not begin until minutes before actual delivery.
Determining the onset of labor in non-human females may be even more unpredictable due to the inability of the animal to discuss its condition with its human caregivers. As with human labor, complications are possible which endanger both mother and children.
Once dilatation has begun, it may not proceed in a linear fashion, requiring medical personnel to repeatedly measure the amount of dilation which has occurred. In standard procedures, this involves the insertion of fingers or instruments into a woman""s vagina to take measurements, taxing the time of busy personnel and the patience of the patient who is in an already uncomfortable state.
Numerous attempts have been made to provide means by which onset and conditions of labor may be evaluated and/or monitored. For example, U.S. Pat. No. 5,063,930 to Nucci shows a disposable probe comprising an elongated conduit member made of transparent plastic and having a closed end portion, an external surface and an internal surface defining an enclosed space. An oval hole is provided in the conduit member near the closed end portion and permits the collection of biological fluids. An indicator allows for the determination of the pH of the fluids collected from the vagina.
U.S. Pat. No. 5,807,281 to Welch shows an apparatus for detecting dilation of a cervix by measuring the force exerted by a cervix as it dilates at the onset of labor. The device comprises a ring-shaped element in series with an enclosure that encircles the cervix and is secured thereto by a friction tab. The enclosure contains a detectable fluid or particulate material which is released by the device to signal that the dilation has occurred.
U.S. Pat. No. 5,406,961 to Artal relates to a premature labor monitor system including a pessary having sensing means for determining the dilation and effacement of the cervix of a patient. Sensing means are provided which determine changes in the energy levels transmitted through the cervical tissue as the tissue thins and loses vascularization during the labor process. Signals are transmitted from the pessary to a patient monitor by such means as small data wires or microwave transmission generated by a small transmitter on the pessary.
U.S. Pat. No. 3,768,459 to Cannon et al. discloses a cervical dilation measuring device comprising a signal transmitting device that may be attached to one side of the cervix and a miniature receiving device attached to or placed against the opposite side of the cervix. The intensity of the signal passed from the transmitting device to the receiving device will vary as a function of the distance of separation of the devices indicating the current dilation of the cervix, Similarly, U.S. Pat. No. 5,438,996 to Kemper et al.; U.S. Pat. No. 5,851,188 to Bullard et al. and U.S. Pat. No. 5,713,371 to Sherman et al. disclose devices having transducers which are positioned on the cervix and which utilize ultrasound to determine the dilation of the cervix.
U.S. Pat. No. 4,476,871 to Hon teaches a device for monitoring cervical dilatation during labor comprising an elongated member adapted for positioning between a fetal presenting part and the cervix. Means are provided for measuring the recession of the cervix with cervical dilatation from the elongated member and along the longitudinal axis thereof.
U.S. Pat. No. 5,876,357 to Tomer relates to a labor monitoring system using a probe in the form of a linear caliper-clamp apparatus and a flexible membrane which are manually inserted into the vagina and clamped on the cervix wall. The arms of the caliper straddle the thickness of the cervical wall and the flexible membrane approximates the radius of curvature of the opening of the cervix. Sensors are used to relate this data to a monitoring unit and data processing apparatus such as a computer.
U.S. Pat. Nos. 4,719,925 and 4,682,609 both to Parsons and U.S. Pat. No. 4,207,902 Krementsov each relate to hand-actuated measuring apparatuses having a scissors-like action which may be inserted into the vagina to determine the dilatation of the cervix.
U.S. Pat. No. 3,583,389 to Harvey; U.S. Pat. No. 4,203,450 to Kegel; U.S. Pat. No. 4,055,839 to Skeggs; U.S. Pat. No. 4,264,900 to Charlier; U.S. Pat. No. 4,232,686 to Kammlade, Jr.; U.S. Pat. No. 5,776,073 to Garfield et al.; U.S. Pat. No. 5,450,837 to Garfield et al.; U.S. Pat. No. 5,879,293 to Hojaiban et al. each teach apparatuses which monitor cervical and/or other labor conditions but which are non-invasive, deriving their output from sensors applied on or about the body surface of a female patient.
Despite the teachings of the prior art, a need still exists for a device having means to determine the onset of labor which may be secured rapidly and easily to the female body. Such a device should be capable of providing data regarding conditions relevant to a pregnant female subject""s cervix to medical caregivers. In addition, such a device should not be obtrusively large or unduly delicate in use such that they do not pose a burden to the female patient/subject or suffer damage under normal conditions of use. Moreover, such a device should be capable of notifying the patient or her health caregiver of dilatation of the cervix.
Accordingly, it is an object of the present invention to provide a device which can sense a condition of the cervix of a pregnant female and to convey information regarding the sensed condition to a health caregiver or to the patient herself at the onset of labor.
It is another object of the present invention to provide a device which is manufactured from bio-compatible materials and may be passed safely and quickly into a pregnant female""s vagina and affixed her cervix.
It is an additional object of the present invention to provide a device which is neither obtrusively large nor unduly delicate in use such that it does not pose a burden to the female patient/subject or suffer damage under normal conditions of use.
It is a further object of the present invention to provide a device which may be used with pregnant female subjects who may be human or non-human.
These and other objects of the present invention are accomplished by providing a labor alerting device comprising a hollow housing having a cavity in which an electronic unit is disposed. The electronic unit comprises a tension sensor which is in electronic communication with a transmitter and further comprises a source of electric power. The housing is manufactured from a bio-compatible material and is saucer-shaped. The top surface of the housing has a central hole through which a spindle is inserted. At one end, the spindle is capped with a tension knob and at the opposing end it is connected to the electronic unit. A plurality of sutures terminating at a first end with suture anchors are attached at a second end to the spindle within the cavity, are introduced over suture guides and threaded through respective pores in the bottom surface of the housing. In use, the device is inserted into the vagina of a female subject and is secured to the tissue of her cervix by the suture anchors. The tension knob is rotated to reel in the sutures and to remove slack therefrom. Dilatation of the cervix at the onset of labor causes tension in the sutures exerted on the spindle. The tension sensor translates the tension exerted on the spindle into a trigger signal which is communicated to the transmitter. Thereafter and in response to the trigger signal, the transmitter emits a signal to an auxiliary electronic device such as a pager to notify the patient or her health caregiver that the cervix has begun dilating in preparation for birth.
These and other advantages and benefits of the present invention will become apparent from the Description of the Invention hereinbelow.